Refrigerating apparatus



Feb. 19, 1946. RATAlcZAK 2,395,055

REFR IGERAT ING APPARATUS Filed May- 28, 1941 4 Sheets-Sheet I Feb. 19,1946. F. 1. RATAICZAK 2,395,065

REFRIGERATING APPARATUS I I Filed May 28, 1941 4 sheets sheet 2 Feb. 19, 1946. F. l. RATAICZAK REFRIGERATING APPARATUS Filed May 28, 1941 4 Sheets-Sheet 3 INVENTOR.

1946. F. l. RATAlCZAK 2,395,055

REFRIGERATING APPARATUS Filed May 28, 1941 4 Sheets-Sheet 4 ?atented Feb. 19, 1946 UNITED STATES m orr cs REFRIGERATING APPARATUS Francis 1. Rataiczak, Dayton, Ohio, assignor a General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application May 28, 1941, Serial No. 395,645 21 Claims. (Cl. 62-115) This invention relates to refrigerating apparatus and more particularly to an improved motorcompressor unit for use in a refrigerating system.

One of the objects of this invention is to provide a motor-compressor unit which lends itself to mass production methods.

' tral metal frame.

Still another object of this invention is to simplify and improve the valve construction.

A further, object of this invention is to simplify the assembly of the motor-stator within the motor-compressor housing.

Further objects and advantages of the pres-- ent invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a partly diagrammatic view of a refrigerating system showing the motor-compressor unit in. section:

Fig. 2 is a sectional view of the compressor unit taken on the line 2-2 of Fig. 1;-

Fig. 3 is a plan view of the motor-compressor unit with the cover of the casing removed and with the motor-rotor broken away;

' Fig. 4 shows the construction of the main shaft and the motor-rotor;

Fig. 5 is an enlarged sectional view showing the suction valve assembly;

Fig. 8' is an elevational view of the main casing without the heat radiating fins and with a portion of the casing broken away so as to more clearly show the motor-stator mounting means;

Fig. '7 is a plan view of the main casing and the motor-stator and illustrates the manner in which the main compressor casing is inserted through the motor-stator;

Fig. 8 is an elevational showing the apparatus used for aligning the main compressor cylinder with the motor-stator; and

Fig, 9 is a fragmentary elevational view, with parts broken away, illustrating the apparatus for aligning the main compresso bearing with the motor-stator.

view partly in section In the manufacture of motor-compressor units, it is customary and, in fact, necessary to tolerate small errors in the dimensions and concentricity of various elements. In the ordinary motor-compressor design the accumulation of tolerances materially affects the efliciency of the unit and frequently renders the unit completely inoperatlve, in which case, it becomes necessary to reoperate some of the parts or to match certain parts with other parts in which the dimensional errors balance out upon assembly. This is especially true in case the compressor and its associated motor-rotor is assembled with a stator which is not perfectly concentric with the main bearing due to tolerances necessary in the manufacture of the stator or due to a slight error in the manufacture of the stator mounting means or due to an accumulation of errors in the motor-stator and its mounting means.

Referring now to Fig. 1 of the drawings, in which I have shown a preferred embodiment of my invention,- reference numeral i0 designates generally a hermetically sealed motor-compressor unit. Reference numeral l2 designates a'substantially cup-shaped stamped sheet metal casing which forms the main support for the compressor assembly- II and also the motor-stator l6. Reference numeral l8 designates a conventional motor-rotor. A stamped sheet metal end cap I! closes the upper end of the cup-shaped casing element 12 and forms therewith a high pressure refrigerant vapor chamber. The end cap I1 is welded or votherwise secured to the main casing i2. Heat conducting fins 2| may be secured'to the outside of the casin element I2 to help dissipate the heat. The high pressure gas flows to the condenser 20 .in which it is condensed and collects in liquid phase in the receiver 22. The liquid refrigerant flows from the receiver 22 into the evaporator 24 through a conventional refrigerant flow control device 25. The

refrigerant flow control device may be of any.

conventional constructionfand is preferably of the fixed restrictor type in which the high pressure liquid refrigerant is required to flow through a long narrow capillary passage.

. to stop the flow of solid particles into the main compressor. As best shown in Fig. 5, the upper side of the adapter block 32 is provided with a recess-3i in which acheclr valve, generally desi The check valve 38 comprises an element 48 provided with a valve seat 42 at its upper edge and otherwise secured to the bottom wall of the casing I2. The upper surfaces of the blocks 32 and 39 are machined so as to be perpendicular to the motor-stator support surfaces described hereinafter. The stamping M, in turn, holds the valve element 48 in place. By virtue 'of this arrangement no special fastening means is required and in the event of valve failure, the damaged valve part or parts may be replaced with a minimum amount of difliculty.

As best shown in Fig. 1, the compressor assembly I4 comprises a lower end plate 58, a cylinder element 52 and an upper end plate 54 which has formed integrally therewith the main bearing 55. The upper end plate 54, as shown in Fig. 3. carries a conventional discharge valve assembly 58 which controls the flow of refrigerant through the compressor outlet 58 provided in the end plate 54. An impeller 62 is provided within the cylinder 52. The impeller 62 is mounted on the eccentric 64 which causes the impeller to compress the refrigerant in accordance with wellknown practice.

A divider block 86 cooperates with the cylinder 52 and the impeller 62 in accordance with wellknown practice. A spring 68 biases the divider block into engagement with the impeller 82. The oliter end of the spring rests against the spring retainer 18. The retainer 18, as shown in Figs. 2 and 3 is provided with a pair of arms l2 having bent end portions which interlock with the holes or keyways I6 drilled in the cylinder element 52. The spring retainer I8 is slipped into place before the cylinder 52 is clamped between the end plates 58 and 54 and is held in place by the end plates 58and 54.

The end plate 58 is provided with a tapered passage 78 which conveys the low pressure refrigerant vapor from the inlet valve 38 to the compression chamber 88. By virtue of the taper in the walls of the passage '58, any slight misalignment between the end plate 58 and the inlet valve 38 will notinterfere with the free flow of refrig erant from the inlet valve to the compression chamber.

Referring to Fig. 2, it will be observed that the inlet port I8 enters the compression chamber 88 at a point close to but spaced from the divider block 86 and spaced from the inner wall of the cylinder element 52. It will also be observed that pressure relief notches 82 have been provided in the cylinder-wall 52 adjacent the divider block 66. By virtue of the inlet port'arrangement, the inlet port is completely closed during the final portion of the compression stroke with the result that it is impossible'ior any of'the compressed gas remaining in'the pressure relief cavityto reexpand into the intake port 18. l

The adapter block 32 is provided witha refrigerant charging plug 84 which has a first passage 7 86 communicating with the compressor inlet passage 38 and a second passage 88 communicating with a passage 88 in the adapter block 32.

"' The lower end plate 58 of'the compressor is cut away as at 92 so as to provide a passage from the "nated by the reference numeral 38 is mounted.

high pressure refrigerant chamber to the passage 98 and the passage 88. The outer ends of the passages 86' and B8 are sealed by means of a plug 94 and a lead-plated copper gasket 96. The gasket 95 is provided with apertures 98 in alignment with the passages 86- and 88. The plug 94 is provided with a single passage I88 through which reirigerant and/or lubricant may be added to-or removed from the refrigerant system upon partially unscrewing the plug 84. By virtue of this arrangement, both the high side and the low side of the refrigerating system may be very quickly evacuated prior to charging the system with reirigerant and lubricant.

The motor-stator I6 is held in rplace by means of special clamps such as I82. The clamps I82 are initially formed as shown in Fig. 6; and are spot welded or otherwise secured to the shell I2. In the prior art devices, it is'customary to .provide a press fit between the outer shell of the compressor and the motor-stator. 'In such an arrangement, it is very difilcult to properly hold the motor-stator in place unless a very heavy cast iron frame or the equivalent is used; and once the motor-stator is in place, it is very diii'icult to remove it for inspection or repair purposes. By virtue of the clamping arrangement shown, a light weight sheet metal casing may be used and the final sizing operation may be performed merely by forcing a die of proper size into the opened end of the casing so as to deform the projecting portion I84 of each clamp I82 the necessary amount. This arrangement of parts and method of sizing eliminates the necessity for as turning the inner surface of the outer shell I2 to size on a lathe. Furthermore, the clamping elements I82 serve to compensate for any taper or irregularity in the walls of the shell I2. It is difiicult'to form the outer sheet'metal casings to any exact dimension since the strains and stresses in the sheet metal casing produced by the drawing operation tend to distort the walls of the casing. The clamps I82, however, sumciently compensate for such distortions.

After the motor-stator has been inserted in place, the projecting ends I86 of the clamp elements I82 are bent over onto the upper side of the motor-stator so as to hold. the motor-stator in a fixed position. This not only reduces the cost of construction and facilitates the assembly of the apparatus, but also'facilitates the removal of the motor-stator in the event that it becomes necessary to replace the motor-stator. The lower ends of the clamps I82 are provided with ears I81 which limit the downward movement of the motor-stator.

The cover member I! is provided with fittin II 8, through which the compressed refrigerant leaves the unit I8. The fitting II8 serves as a stop for limiting the axial movement of the motor-rotor I8 and the shaft I9 during shipment, etc. During normal operation, the shaft I9 is spaced from the adapter II8 as shown in Fig. 1.

In order to avoid the harmful accumulation of tolerances in dimensions in assembling the-various parts, the various parts of the unit are assembled in the following mannen, In assembling the various elements that go to make up the compressor unit, the first step is to position the cylinder 52 with respect to the lower end wall 58. This is done by means of a conventional positioning mandrel (not shown) which holds the member 52 in proper alignment with the member 58 while one or more bcltssuch as bolt I58 (see Fig.

75 3) is or are tightened so as to clamp the elev ments 56 and 52 together in their proper relationship. After the elements 56 and 52 have been fastened together in proper alignment, the impeller 62, the divider bolck 66, the divider block spring 66 and the spring retainer 16 are inserted in place and the upper end plate 54 is bolted to the cylinder 52 and the lower end plate 50 by means of bolts 51. A positioning mandrel (not showm is used for holding the end plate 54 in alignment while the bolts 51 are being tightened.

The compressor assembly may then be inserted downwardly through the opening in the motorstator as shown in Fig. '1. The compressor assembly is of such shape and size that it may readily pass through the opening in the motor-stator. -After the compressor assembly has been slipped into place in the bottom of the casing I2, a specially constructed positioning fixture I52 is used for aligning the main compressor bearing with the inner surface of the motor-stator.

The positioning fixture I52 comprises a central 'the cap screws 56 are tightened. This serves to J Atfer removal shaft I54 provided with a knurled handle I56.

The main portion of the central shaft I54 has a diameter corresponding to the internal diameter of the main compressor bearing 55. Another Portion- I58 of .the central shaft I54 has a diameter slightly less than the internal diameter of the impeller 62. The lowermost portion I60 of the central shaft I54 has a diameter corresponding to the internal diameter of the bearing provided in the lower end plate 50 for the lowermost portion 23 of the main compressor shaft I9. The positioning fixture I52 as an intermediate sleeve member I62 which is slidably mounted on the central shaft I54. The intermediate sleeve S62 is provided with a knurled handle portion.|64. The lower end of the sleeve I62 is tapered for a purpose explained hereinafter. The main body I66 of the positioning fixture I52 has a central aperture through which the sleeve I62 and the shaft I 54 may be inserted.. The outer diameter of the main portion of the element I66 is slightly less than the internal diameter of the motorstator I6. 1

As best shown in' Fig. 9, the main body I66 of the positioning fixture is provided with four longitudinally extending slots I68 in each of which is mounted a shoe element I16. Each shoe element I10 is provided with a shank- I12 which passes through-a radially extending hole I14 formed in the body I66. The inner end of each shank is provided with a cam surface I16 which is adapted toengage the tapered portion of the sleeve I62; The element I66 is provided with a shoulder I16 which limits the movement of the element I66 within the motor-stator I6. The arrangement is such that when the posttioningflfixture is inserted into the motor-stator and .the sleeve element 162 is-moved into the position in which it is shown in Fig. 8, the sleeve I62 cams the shoes I16 into engagement with the motor-stator, whereby the central shaft I54 of the positioning mandrel may be used for lin ing up the compressor assembly with respect to the .motor'-stator-. 6 l

The main body I66 of the positioning fixture.

is provided with a plurality of apertures I66 of the motor-stator whereby the mandrel may beremovedwlthout difllculty.

,In the event that the upper surfaces of the block 36 and the adapter element 32 are not perpendicular to the inside walls of the motorstator, the positioning mandrel will bind when give notice that the proper perpendicularity is lacking so that the compressor assembly may be immediately removed and the parts reoperated so as to obtain theproper perpendlcularity. of the positioning mandrel I52, the motor-rotor I6 and its associated shaft I9 may be dropped into place.

Inasmuch as the above described construction allows the motor-rotor to be secured to the shaft I9 priorto the assembly of the shaft in the main bearing, it is possible to true-up the outer diameter of the motor-rotor after it has been mounted on the shaft, thus eliminating the accumulation of tolerances in the concentricty of the main shaft,- the internal bore of the motor-rotor and the external diameter of the motor-rotor.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows: l. A motor-compressor unit comprising in combination; astamped sheet metal shell member; motor-stator clamping means. secured to the inner wall of said shell member; a motor-stator supported by said clamping means; said clamping means comprising integrally formed motorstator positioning lugs; compressor mountin means carried by one wall of said shell having.

one surface arranged perpendicular to the inner surface of said motor-stator; a motor-rotor; a"

first passage communicating with the outlet side" of said compressor and including a second passage communicating with the inlet side of said compressor; and removable plug means accessible from outside of said shell member sealin 1 said passages; said plug means having a passage formed therein adapted to communicate with both the said passages upon partial removal of said plug.

2. A motor-compressor combination, a stamped sheet metal shell member, sheet'metal motor-stator clamping means secured to the inner-wall of said shell member.

a motor-stator supported by said clamping means, said clamping means having integrally formed motor-stator positioning lugs, comthrough which access vmay be had to the cap;

screws 66 which secure the compressor assembly to the mounting blocks 62 and 69. While the positioning fixture-is in place, the cap screws 66 are securely tightened so as to rigidly hold the compressor assembly in position. After having tightened the cap screws 66,the positioningmandrel is removed. "37 removing the sleeve pressor mounting means carried by one wall of said shell having one surfce arranged perpendicular to the interior surface of said motorstator, a recess in one of said mounting means. valve means within said recess, a compressor assembly secured to said mountingmeans and servingto' hold said valve means in said recess.

refrigerant charging means provided by said compressor mounting means, said charging means including a first passage communicating with the outlet side'of said compressor and ineluding second passage communicating with unit comprising in the inlet side of said compressor, removable plug means sealing said passages, said plug means having a passage formed therein adapted to communicate with both the said passages upon partial removal of said plug.

-3. In a refrigerant compressor, a cylinder member having a divider block slot, a pair of holes drilled in said cylinder member adjacent said divider block slot, a divider block within said slot, a divider block spring engaging one end of said divider block, spring retaining means engaging said spring for holding said spring in place comdrilled in said cylinder member adjacent said divider block slot, a divider block within said slot, a divider block spring engaging one end of said divider block, spring retaining means engaging said spring for holding said spring in place comprising a substantially U-shaped element havin its arms interlocked with said holes, a pair of compressor end plates secured to said cylinder and clamping said u-shaped member in position, a compressor shaft journaled in one of said end plates, animpeller eccentrically mounted on said shaft and having contact at its periphery with the end of the divider block remote from the divider block spring. inlet and outlet ports on opposite sides of said divider block, a casing, mounting means for said end plates and said cylinder carried by one wall of said casing for supporting said cylinder and end plates within said casing, and means for holding said cylinder, end plates and mounting means in assembled relationship comprising a plurality of cap screws engaging said mounting means. I

5. In a refrigerant compressor, a cylinder member having a divider block slot, a pair of holes drilled in said cylinder member adjacent said divider block slot, a divider block within said slot, a divider block spring having one end engaging one end of said divider block. spring retaining means engaging the other end of said spring for holding said spring in place comprising a substantially U-shaped element" having the arms thereof disposed on opposite sides of said spring and interlocked with said holes, a pair of compressorend plates.v secured to said cylinder and clamping said U-shaped member in position,

inlet and outlet ports on opposite sides of said divider block an impeller within said cylinder,

7 said impeller being arranged in engagement with the other end of said divider block, and a comsaid impeller and removably iournaled in said end arms thereof interlocked with said holes, a pair of compressor end plates secured to said cylinder and clamping said U-shaped member in position, an impeller within said cylinder, a compressor operating shaft removably journaled in said end plate members whereby said shaft may be assembled after said end plates have been secured to said cylinder, a casing, compressor mounting means within said casing, means for securing one of said end plates to said compressor mounting means, said compressor mounting means including one portion projecting through one wall of said casing and having a refrigerant flow passage therein for conveying refrigerant through the wall of said casing, a valve mounted in said refrigerant flow passage for preventing flow of refrigerant through said passage in one direction, said valve being held in place by meansof one of said compressor end plates, refrigerant charging passages in said one portion of said compressor mounting means, and one of said passages com- .municating with the inlet side of the compressor and the other of said passages communicating with the outlet side of the compressor.

7. In combination, a casing, a compressor mounting element projecting through the wall of said casing, a refrigerant compressor supported 'within said casing on said mounting element, said compressor having an inlet and an outlet, said mounting element having a first passage for conveying refrigerant to be compressed from without the casing to the inlet of said compressor, and means in said element for supplying refrigerant to both the inlet and outlet sides of said compressor simultaneously including a second passage in said element leading to the outlet side pressor operating shaft drivingly connected to plate members whereby said shaft may be assembled-after said end plates have been secured to said cylinder. 6. -In a refrigerant compressor, a cylinder member having a divider block slot, 1:. pair of holes drilled in said cylinder member adjacent said divider block slot. a divider block'within a divider block spring engaging one end of said divider block, spring retaining means comprising a substantially U-sbaped element havin the said slot,

of said compressor.

8. A combined refrigerant compressor mounting means and refrigerant charging plug for use with a compressor enclosed within a casing which comprises, an element having one portion disposed outside of the compressor enclosing casing and a'second portion disposed within the compressor enclosing casing and serving to hold the compressor in fixed relationship to said casing, a first'passage in said element for supplying refrigerant to be compressed to said compressor, and a second passage in said element for adding refrigerant to the compressed refrigerant leaving said compressor.

9. A combined refrigerant compressor mounting means and refrigerant charging plug for use with a compressor enclosed within a casing which comprises, an element having one portion disposed outside of the compressor enclosing casing and a second portion disposed within the compressor enclosing casing and serving to hold the compressor in fixed relationship to said casing, a first passage in said element for supplying refrigerant to be compressed to said compressor, a second passage-in said element for adding refrigerant to the compressed refrigerant leaving said compressor, and a check valve disposed within one of said passages.

10. A combined refrigerant compressor mounting means and refrigerant charging plug for use with a compressor enclosed within a casing which comprises, an element having one portion disposed outside of the compressor enclosing casing and a second portion disposed within the compressor enclosing casing and serving to hold the ing block means,

motor stator has been mounted in place for ading in said v the main support for holding the motor stator shaped casing formed of;

assumes erant tothe compressed refrigerant leaving said compressor, and 'acheck valve disposed within one of said passages and clamped in place between the compressor and said element. I

11. In a sealed motor-compressor unit, a cupshaped casing of stamped sheet metal material, a 'motor including a motor stator supported by said casing in the upper portion thereof and provided with a central opening, a compressor driven by said motor disposed within the lower portion of said casing, compressor mounting block means carried by said casing providing a flat upper surface engaging the bottom side of the compressor, said compressor being adJustable sidewise on said block means relative to said motor stator whereby said compressor may be properly aligned with the central opening of said motor statorafter the motor stator has been fixed in place, and means for holding the compressor in alignment with said central opening. 1

12. In a sealed motor-compressor unit, a cupshaped casing, a motor including a motor stator supported by. said casing and provided with a central opening, a rotary compressor driven by said motor and having a flat end surface, com pressor mounting block means carried by said casing providing a flat compressor engaging surface, said compressor being adjustable sidewise on said mounting block means relative to said motor stator whereby said compressor may be properly aligned with the central opening of said motor stator after the motor stator has been fixed in place, and means for holding the compressor in alignment with said central opening. v

13. In a sealed motor-:compressor unit, a cup- .shaped casing section formed of stamped sheetmetal material, a motor stator disposed substantially within said section, embossed sheet metal motor stator mounting means between said casing section and said motorstator compensatin for irregularities in said casing section, com-- pressor mounting block means secured to said driven by said shaft, first bolt means holding one ported by said casing;

material; a motor includinga motor stator supcompressor mountin meansjsecured to the bottom wall of said casin a compressor assembly comprising a cylinder, top and bottom end plates. for said cylinder having shaft bearing apertures therein, ashaft driven by said motor, an impeller between said end plates end plate and said cylinder together as a unit in proper alignment, second bolt means holding the cylinder, the impeller, and the two end plates together as a unit with said bearing apertures inalignment with one another; and third bolt means for adjustably holding said last named unit in place on said compressor mounting means whereby said compressor assembly may be adjusted sideways on said compressor mounting means independently of said motor stator.

16. In a motor compressor unit, an outer shell having a lower cup-shaped portion formed of stamped'sheet metal andan upper lid portion secured to said lower cup-shaped portion, a pinrality of compressor mounting blocks secured to one wall of said lower portion, a motor stator,

means for mounting'said motor stator in said lower shell portion, a compressor assembly and a motor rotor adjustably mounted on said mounting blocks whereby said compressor assembly may casing section having a flat compressor mount ing surface, a compressor assembly adjustable sidewise on said surface and having a removable driveshaft, a motor rotor carried on said drive shaft, said compressor assembly comprising a cylinder member and a pair of-end plates held together as a removable unit by means of a plurality of bolts, and additional bolts for adjustably securing saidassembly in proper alignment with said motor stator.

14. In a sealed motor-compressor .unit, the combination of acup shaped casing of stamped sheet metal material, a motor including a motor stator'supported in the upper portion of said casing andhaving a central opening, a comprescompressor assembly be adjusted on said mounting blocks so as to be in aligmnent with the motor stator surfaces. em bossed sheet metal spacer means between said motor stator means and said shell compensating for irregularities in said stamped sheet metal,

- said spacer means including means for preventregularities in said stamped sheet metal shell and serving to convey motor heat'to the outer shell, said compressor mounting means including means for adjusting the position of said compressor relative to said motor stator after said motor stator has been fixed in place.

18. In a motor compressor unit, an outer shell ,formed of stamped sheet metal material, a comsor driven .by said motor having a flat bottom surface and having shaft bearing surfaces arranged perpendicular to the bottom surface, compressor mounting block means secured to the bottom wall of said casing andproviding a flat upper surface for engagement with'the bottom surface of said compressor without limiting side wise movement of said compressor on said mountand means accessible after the .iustably securing the compressor in place on said mounting block means with the shaft bearing surfaces arranged concentric to the centralopenmotor stator, said casing serving as and the compressor in fixed relationship.

15. In a sealed motor-compressor unit; a cupstamped sheet metal,

. venting endwise movement of said motor stator both said passages upon pressor, means for mounting said compressor within saidshell, a motor in driving engagement with said compressor including a motor stator,-

embossed sheet metal spacer means between said motor stator and said shell compensating for irregularities "in said stamped sheet metal shell,

said spacer means including integral lugs for prein said shell. 1

19. In combination, a

having an inlet and an outlet. adapter means projecting through said casing and having a first passage communicating with the inlet to said compressor and a second passage communicating with the outlet of said plug. having a passage to communicate with partial removal of said of said passages. formed therein adapted x casing, a compressor -.supported within said casing, said compressor said compressor, and a plug accessible from outside of said casing sealing both 20. In combination, means forming a compressor cylinder, end plates for closing the ends of said cylinder, a divider block slot in said cylinder, a divider block slidably mounted within said slot, spring means biasing said divider block inwardly, keyways formed in the outer wall of said cylinder and arranged substantially parallel to the axis of said cylinder, spring abutment means in engagement with the. outer end of said spring means and including arms slidable downwardly through the keyways provided in said cylinder wall, said keyways and said arms being so constructed and arranged that the arms are locked in place by said end plates, a drive shaft rotatably mounted within the compressor cylinder, an impeller eccentrically mounted on said shaft and having contact at its periphery with the end of the divider block remote from the spring means, and fluid inlet and outlet ports in the compressor cylinder on opposite sides of the divider block.

21. In combination, means forming a compressor cylinder, end plates for closing the ends 01 said cylinder, a divider block slot in said cylinder, a divider block slidably mounted within said slot,

spring means biasing said divider block inwardly,

keyways formed in the outer wall of said cylinder, spring abutment means in engagement with the outer end of said spring means and including arms insertable into the keyways provided in said cylinder wall, said keyways and said arms being so constructed and arranged that the arms are interlocked within said keyways, a drive shaft rotatably mounted within the compressor cylinder, an impeller eccentrically mounted on said shaft and having contact at its periphery with the end of the divider block remote from the spring means, andvfluid inlet and outlet ports in the compressor cylinder on opposite sides of the divider block.

, FRANCIS I. RATAICZAK 

